We must first establish the underlying, persistent authority of the Old Testament and only then ask whether that authority has specific prescriptive application to ourselves. Let us make it clear in no uncertain terms that the enduring authority of the Old Testament is a fundamental requirement for canonicity, for interpretation, and for application (2 Timothy 3:16). In every circumstance we are beholden to the foundational nature of the Torah for our initial guidance. In our individual lives and in history, humans learn what is good and proper by observation first.
The law of God, wherever it appears in Scripture (from Genesis to Revelation), always displays the character of God applied to human affairs. This is as true of Genesis 9 as of Exodus 20, and of Leviticus 23 as of Matthew 5-7.
While a specific case law instantiates a particular enduring ethical principle, the transitory specificity of the case does not obviate the enduring application of the moral law. So, for example, while we no longer use flat roofs for hosting social gatherings, I remain constrained by Deuteronomy 22:8 to salt my sidewalks when icy and to put a fence around my swimming pool, and if it should become the case that roofs once again become a common gathering place, I will once again be commanded to build a parapet around my roof.
Furthermore, this case law has civil import. We are instructed in the proper extent of civil government by Deuteronomy 22:8, which has no penalty for failing to build a parapet, unless someone dies as a consequence of not having done so, in which case the negligent offender is guilty of manslaughter. While it is accurate to recognize that we are no longer commanded that each contemporary government should make it a law that roofs have parapets, each government is commanded to punish those who fail to love their neighbor in such a way that the neighbor is harmed.
Furthermore, that same government is constrained from interfering until such harm occurs: the civil government is given the sword: “an avenger who carries out God’s wrath on the wrongdoer.” (Rom 13:4).
It is essential we recognize that the Apostolic Scriptures introduce no innovation, rather they reveal what has always been but was not recognized. They amplify what has been previously declared, revealing what has always been the intent. Nothing is overturned by the Apostolic writers, rather the deeper and the broader is revealed, hidden as it were, among the already declared. We see above how Romans 13:1-8 amplifies the content contained in Deuteronomy 22:8.
Jesus’ walk with his two disciples on the road to Emmaus is the quintessential display of the New Testament’s function. At first sight, the two disciples do not recognize Jesus in front of their eyes, but, “beginning with Moses and all the Prophets, he interpreted to them in all the Scriptures the things concerning himself” (Lk 24:27).
There is a primary and essential continuity between the Hebrew and the Apostolic scriptures, and there is no division between law and grace except in function. The law on its own multiplies sin and condemns the sinner, but the law when paired with grace is no longer “the law of sin and death” but “the law of the Spirit of life. (Romans 8:2). It is, indeed, the same law, but transformed in function; it no longer condemns but now guides the redeemed and regenerate man, and to the Spirit-enlivened eyes it now illumines the way of Christ. So could David exclaim, “Oh how I love your law,” and “In the way of your testimonies I delight as much as in all riches” (Psalm 119:97,14). “I will run in the way of your commandments when you set my heart free!” (Psalm 119:32).
No sooner have I penned these words then I hear the forthcoming chorus of “buts.” “But Acts 10.” “But Romans 14:14.” Yes, and but Colossians 2:16-17, but Romans 10:4, and Galatians 3:13. And I might reply “but Matthew 5:17 and Romans 7:12.” BUT, the solution is not in pitting these passages against each other, but in finding the simplest and most contiguous reading that allows these passages to faithfully complement one another. In obedience to the laws of hermeneutics and of logic (that we might not multiply complexity beyond necessity), we ought to read these passages, so far as possible, through the eyes of their initial recipients, never permitting our interpretation to cause contradiction among them, and never allowing our interpretive understanding to undermine corollary principles, e.g., the rules of canonicity, or credulity.